Method and device for winding a yarn

ABSTRACT

In application of the stepped precision winding process for winding, the rotational speed of a traverse motor is derived directly from the rotational speed of the bobbin chuck. The rotational speed is derived, preferably, using the instantaneously valid winding ratio which, in turn, is determined in relation to the crossing angle.

FIELD OF THE INVENTION

The invention concerns a method and a device for winding yarns on to atube by means of the so-called stepped precision winding principle.

BACKGROUND OF THE INVENTION

DOS 3332382 demonstrates a winding device designed for building a bobbinby means of the stepped precision winding process. In particular, thisDOS proposes the input of winding ratios into a memory which are thenretrieved as required during the bobbin travel. A "step" from onewinding ratio to another is initiated in relation to the determinedACTUAL value of the crossing angle of the bobbin--see FIG. 3 of the DOSdocument.

EP-C-64579 demonstrates another machine which is suitable for windingaccording to the stepped precision winding process. The winding ratiosare again stored in memory as (M/N number pairs). In this case the stepsare tripped in relation to the diameter of the bobbin (see FIGS. 7 to 9and the corresponding description on page 7 of the EP PatentSpecification).

SUMMARY OF THE INVENTION

The invention proposes, as a first aspect, a method for building apackage with a stepped precision winding system, whereby the windingratio is changed when the crossing angle assumes a predetermined value,characterized in that the crossing angle is determined by comparison ofcircumferential speed of the package with a value derived fromrotational speed of the package.

The invention proposes, as a second aspect, a method for building apackage with a stepped precision winding system characterized in that asignal for controlling the traverse is obtained by the adaptation of achuck rotation signal in relation to a predetermined winding ratio,whereby the predetermined winding ratio is determined in relation to theinstantaneously determined crossing angle.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention is described in greater detail with reference embodimentsas examples.

FIG. 1 shows a view of a winder, at the bobbin side,

FIG. 2 shows a cross-section through the contact roller and the bobbinchuck at the start of winding, in accordance with our EP Patent 200234,

FIG. 3 shows an example of a possible circuit arrangement for activatinga means for regulating the rotational speed of the bobbin chuck, similarto FIG. 6 of U.S. Pat. No. 5,462,239 of 23.07.1992,

FIG. 4 shows a representation of the frequency curve of the contactroller following activation by "detuning" of the contact rollerfrequency by the bobbin, similar to FIG. 7 of U.S. Pat. No. 5,462,239,

FIG. 5 shows a schematic representation of the signal connection betweenthe bobbin chuck and the traverse of the machine according to thisinvention,

FIG. 6 is a diagram illustrating the application of the steppedprecision winding process according to this invention,

FIG. 7 shows a schematic representation of further details of thearrangement as in FIG. 5,

FIG. 8 is a diagram illustrating the crossing angle progression.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, Ref. 1 indicates a high-speed winder for, in particular,synthetic filaments. For the purpose of simplifying the description onlyone yarn path is shown. In practice, on machines of this type up toeight bobbins are arranged adjacent to each other on each chuck. Theconstruction of the machine 1 is that known in the art, such as thatdescribed for example in the above-mentioned European PatentSpecification No. 0200234.

For the same reason of simplification, only the elements which areessential to the description of the invention are shown in the figure.Ref. 3 is the casing of the machine 1. A revolver 5, which swivelsaround an axis 7, carries a chuck 9 at each end, a tube 11 being mountedon each chuck. The lower chuck 9 is shown with the package 10 of a fullbobbin 13; only a very small quantity of yarn has been wound on to theupper tube 11, this yarn being scarcely visible in FIG. 1. The yarn 15which runs from the top is passed backwards and forwards by a traversedevice 17, passing around a tacho or contact roller 19 before reachingthe tube 11. FIGS. 1 and 2 show, at the start of the winding process, agap "S" between the contact roller 19 and the surface of the tube 11.Following winding of a certain quantity of yarn on to the tube 11, thisgap is closed up and then disappears. The size of the gap "S" is presetand depends upon the rotational speed of the contact roller 19 and,consequently, the winding speed of the machine as well as the yarn countand other characteristics of the yarn 15 which is to be wound.

The gap "S" is not material to this invention but it must neverthelessbe taken into account, where such a gap exists, because control of thewinding process according to the preferred design can only occurfollowing contact between the package and the contact roller.

The contact roller 19 and the traverse device 17 are mounted in acantilever bracket 21 which is moved vertically by the guide 23.

The initial winding of the yarn 15 on to the tube 11 without contactwith the contact roller 19 has the advantage that there is no resultant"milling" and rubbing of the contact roller 19 and the tube 11 andtherefore there can be no damage to the outer layers of the yarn 15wound on to the tube 11. The time until the gap "S" is filled isdetermined by means of a previously calculated rotational speed ramp,i.e., a rotational speed progression which reduces the rotational speedof the bobbin chuck 9 as the diameter of the bobbin package 13increases, to a point at which the two surface speeds are theoreticallyidentical--when the gap "S" is filled and there is contact between thetwo surfaces. This, however, is only theoretically possible, due to awide variety of parameters, such as the quality of the yarn 15, the yarncount, etc.

The automatic software control process for changing the speed ramp usingdetuning is illustrated and explained with reference to a possible"circuit" as in FIG. 3. In practice, this "circuit" is "embodied" in thesoftware of the machine control system.

At the start, the setpoint generator 25 receives setting values for thecontact roller 19, for both a winding speed VTW and a correction factorwhich controls the circumferential force, as described, for example, inEP-A-182389. Since an asynchronous motor is used as the contact rollerdrive motor 37, the contact signal (frequency F tacho) differs from thecontact setpoint. However, the absolute value of the frequency (F tacho)is not significant for monitoring by the monitoring device 27. Followinga time delay such that the contact roller 19 rotates at the startingspeed, the chuck drive motor 35 is switched on by the control system andlikewise brought to the starting speed, at which point the yarn can bedrawn in.

When the yarn is drawn in, the monitoring device 27 switches on the rampgenerator 39 which delivers its output frequency to the frequencyconverter 33. The device 27, and the ramp signal generator 39, whichdetermines the rotational speed progression of the bobbin chuck 9, eachseparately receive a signal when the yarn is drawn in. The controller 31is deactivated at this point, since the contact signal (F tacho) cannotbe used for servo control.

Following contact by one or more bobbin packages with the contact roller19, the contact frequency deviates from its starting value. Thisdeviation is detected by the monitoring device 27 which then switchesoff the ramp generator 39 and activates the controller 31. Thecontroller 31 then brings the chuck speed VTW back to a value whichproduces a predetermined control frequency (the control frequency beingin conformity with the set value for the bobbin speed).

The deviation from the starting value must attain a magnitude such thatan essentially slip-free frictional connection is established betweenthe surfaces of the contact roller 19 and the package 10 on the bobbin11. Minor disturbance effects can be disregarded. It is also possible tobuild in a time delay after the detection of the deviation for thepurpose of ensuring that the conditions for the essentially slip-freefrictional connection between the surfaces of the contact roller 19 andthe bobbin package 10 have been fulfilled so that an unambiguousmeasurement value is obtained from the contact signal for the actualbobbin speed VDO.

The deviation from the starting value can occur as described above (FIG.4) or as described below (no figure). The control frequency can be aboveor below the starting frequency, or it can be equal to the startingfrequency.

The following description assumes that the gap has been filled up, or isnot present at the start of the bobbin building process. In the lattercase, contact between the contact roller and the package exists from thestart.

FIG. 5 shows, in schematic form, further details of the drives for thedifferent fundamental components of the machine. These componentscomprise:

the contact or tacho roller 19 with its drive motor 37,

the bobbin chuck (not shown in FIG. 5) in the winding position, with thepackage 10 and its drive motor 35, and

the traverse device 17 with its drive motor 40.

Ref. 41 designates the machine control system as a complete unit. Therepresentation in FIG. 5 bears no relation to the geometry of the actuallayout of the machine (FIG. 1) since FIG. 5 serves to illustrate signalconnections rather than the spatial form of the machine.

The motor 35 and the motor 37 are each equipped with a tacho signalgenerator, 42 and 43 respectively, which generates a signal whichrepresents the rotational speed of the motor or the speed of the axledriven by the motor. These signals are delivered to the control system41. The control system 41 generates a signal which is supplied to themotor 40 (or to a controller, not illustrated, for the motor 40) for thepurpose of determining the rotational speed of this motor. Thisdetermines the movement of the yarn guide or guides.

The theory of stepped precision winding, as embodied here, has beenexplained in DOS 3332382 and is not repeated in this document. Theeffect is summarized in FIG. 6. The horizontal axis of the diagram givesthe bobbin diameter (the axis does not start from "zero" because a"bobbin travel" commences at a minimal bobbin diameter which is given bythe diameter of the empty tube 11, FIG. 1). The vertical axis gives thebobbin crossing angle.

It is a characteristic of a precision winding system that the crossingangle decreases as the bobbin diameter increases if the winding ratio(the number of forward-and-back cycles of the yarn guide per bobbinrotation) remains constantly unchanged. Curves for constant windingratios are indicated by W.

In a stepped precision winding system, "steps" from a higher windingratio (curve closer to the left-hand corner of the diagram) to a lowerwinding ratio (curve further from the left-hand corner) occur at givenpoints during the bobbin travel.

According to the proposed method, such a step occurs when the crossingangle, in the prevailing winding ratio, drops to a lower limiting valueGu. The magnitude of the step is limited by an upper limiting value Go,which prevents unwanted sudden changes in the bobbin ratios. However,this maximum step magnitude cannot be used without qualification becausethe "valid" winding ratios have to be input to the memory of the controlsystem 41 as single values. Since only a finite number of such windingratios can be stored in the memory, an "existing" value within thelimits Gu-Go must be selected from the memory and applied for a step.

The winding ratios must be precisely determined, to at least four(preferably five) decimal places. In the case of very high deliveryspeeds (bobbin circumferential speeds), building of the bobbin can beimpaired by time lags in the execution of these steps. It is necessaryto avoid, as far as possible, any time lag in the determination of a newwinding ratio in the control system 41 and any inaccuracy in theexecution of a step.

Known in the art is the practice of controlling the traverse speed forthe purpose of obtaining a predetermined winding ratio from the controlsystem 41. The traverse speed must be continuously adjusted because therotation speed of the chuck is reduced as the bobbin diameter increasesin order to keep the circumferential speed of the bobbin constant.

In the design as in FIG. 7, the traverse speed is corrected independence upon to the rotational speed of the chuck, with a feedfrequency for a frequency-controlled drive motor 40 (FIG. 5) beingderived directly from the output signal of the generator 42 (FIG. 5).For this purpose, the control system 41 comprises a multiplicationdevice 44 by means of which the frequency generated by the generator 42is multiplied by a factor "X". The output signal of the device 44 istransferred to a frequency converter 45 as a control signal anddetermines the output signal of the power section of the converter 45.The latter output signal is delivered to the motor 40 (FIG. 5) as a feedfrequency and determines the rotational speed of this motor. The motor40 can be, for example, a synchronous motor.

The use of a synchronous motor, or even a frequency-controlled motor asa traverse drive motor 40 is not a material characteristic of theinvention, since it would be possible to use any other preciselycontrollable motor capable of producing the required power. The controlsystem 41 would then have to produce a control signal suitable for themotor controller.

The factor X corresponds to the prevailing winding ratio. In a "step",the prevailing factor must be replaced by a new factor which has to beretrieved from the above-mentioned memory 47 and input to the device.The replacement of one factor by a new factor can be executed rapidlyand is effective almost immediately for determination of the outputfrequency of the converter 45.

The initiation of a step is important in this connection and here againtime lags are to be avoided as far as possible. A new factor must beselected when the crossing angle falls to a predetermined value, whichmust be monitored. The motor 40 could also be equipped with a tachosignal generator for this purpose, which would be the same as measuringthe crossing angle (cf. DOS 3332382). This, however, necessitates anadditional signal generator and additional signal processing capacity inthe control system 41. Signals which can be used for determination ofthe crossing angle are, however, already present, as in FIGS. 3 and 5,these being the output signal of the device 44 (corresponding to thetraverse speed) and the output signal of the tacho signal generator 43(corresponding to the circumferential speed of the bobbin). The ACTUALvalue of the crossing angle is measured by processing these signals inthe unit 46 (FIG. 7). The limiting values Go, Gu (FIG. 6) can be enteredby the user via a keypad 48 and compared with the ACTUAL value.

Input of a Crossing Angle Progression

The principle of a preferred embodiment for setting a device accordingto this invention is shown in schematic form in FIG. 8.

In order to optimize building of the package, the setpoint crossingangle can be determined as a function of the bobbin diameter. Theprogression of the setpoint curve is determined using four base pointsSP0, SP1, SP2 and SP3 and the bandwidth B.

The base points are defined as follows:

    ______________________________________                                        SP 0: Tube diameter (fixed)                                                                   /Crossing angle 0                                                                          (example:                                                                     106 mm/14°)                               SP 1: Change point angle 1                                                                    /Crossing angle 1                                                                          (example:                                                                     150 mm/15°,                                                            75°)                                      SP 2: Change point angle 2                                                                    /Crossing angle 2                                                                          (example:                                                                     250 mm/14°)                               SP 3: Bobbin diameter                                                                         /Crossing angle 3                                                                          (example:                                                                     420 mm/14°)                               ______________________________________                                    

In this case, where the required crossing angle changes over the bobbintravel, the instantaneously prevailing set value for the crossing anglemust be determined by the control system by determination or measurementof the bobbin diameter. This gives an instantaneously valid windingratio which must then be changed when the effective crossing angledeviates outside the bandwidth.

I claim:
 1. A method for building a package with a stepped precisionwinding system that includes a chuck on which the package is built and atraverse device for moving yarn back and forth with respect to thechuck, comprising:winding yarn on the chuck to build a package;determining a chuck rotational speed to obtain a chuck rotational speedsignal; controlling the traverse device based on the chuck rotationalspeed signal and a set winding ratio; determining the circumferentialspeed of the package; deriving a quantity from the determined chuckrotational speed; determining a crossing angle at which the yarn isbeing wound on the package based on the determined circumferential speedof the package and the quantity derived from the determined chuckrotational speed; comparing the determined crossing angle to apredetermined crossing angle value; and changing the set winding ratioto a different winding ratio when the determined crossing angle reachesthe predetermined crossing angle value.
 2. A method according to claim1, wherein said step of deriving a quantity includes deriving a quantitybased on both the chuck rotational speed and the predetermined windingratio.
 3. A method according to claim 1, including utilizing said chuckrotational speed signal for controlling the traverse and for determiningthe crossing angle.
 4. A method according to claim 1, including enteringsaid predetermined crossing angle value by way of a keyboard.
 5. Amethod according to claim 1, wherein said predetermined crossing anglevalue is a lower limit value for the crossing angle, and includingentering by way of a keyboard said lower limit value for the crossingangle and an upper limit value for the crossing angle, said step ofcomparing the determined crossing angle to the predetermined crossingangle value including comparing the determined crossing angle value toat least the lower limit value.
 6. A winding device for winding yarn tobuild a package, comprising:a chuck on which is to be built a package; achuck drive device for rotating the chuck; a traverse device for movingthe yarn back and forth with respect to the chuck; a traverse drivedevice for moving the traverse device; a signal generator for generatinga first signal corresponding to the rotational speed of the chuck; meansfor determining a circumferential speed of the package; and a controlsystem adapted to generate a second signal based on said first signal,said second signal being used to control movement of the traversedevice, said control system including means for deriving a crossingangle of the yarn being wound based on the determined circumferentialspeed of the package and a quantity derived from the rotational speed ofthe chuck, and for changing a winding ratio when the derived crossingangle reaches a predetermined crossing angle value.
 7. A winding deviceaccording to claim 6, wherein said means for determining thecircumferential speed of the package includes a contact roller with atacho signal generator.
 8. A winding device according to claim 7,wherein the contact roller is driven by a drive motor that is connectedto another signal generator.
 9. A winding device as in claim 6, whereinsaid means for deriving a crossing angle of the yarn being wounddetermines the quantity derived from the rotational speed of the chuckusing a prevailing winding ratio which is predetermined by the controlsystem.
 10. A winding device according to claim 6, including means forentering and changing the predetermined crossing angle value.
 11. Awinding device according to claim 6, wherein said predetermined crossingangle value is a lower limit value for the crossing angle, and includingmeans for entering and changing the lower limit value for the crossingangle and an upper limit value for the crossing angle.
 12. A method ofbuilding a package with a stepped precision winding system having aplurality of stored winding ratios in which yarn is wound with respectto a chuck to produce a package while a crossing angle of the yarnchanges, comprising:entering upper and lower limit values for thecrossing angle to define a desired crossing angle range; selecting awinding ratio; winding yarn onto a tube under the selected windingratio; determining an actual crossing angle of the yarn being wound;selecting a different winding ratio when the determined actual crossingangle reaches one of said upper and lower limit values so that windingof the yarn continues under a new winding ratio, said new winding ratiobeing selected so that the crossing angle of the yarn is within saiddesired crossing angle range.
 13. A method according to claim 12,including determining a rotational speed of the chuck and determining acircumferential speed of the package, determining a quantity derivedfrom the determined rotational speed of the chuck, said actual crossingangle being determined based on the determined circumferential speed ofthe package and the quantity derived from the determined rotationalspeed of the chuck.
 14. A method according to claim 12, includingmanually entering said upper and lower limit values for the crossingangle.
 15. A method according to claim 13, including traversing the yarnback and forth with respect to the chuck by way of a traverse device,and including controlling the traverse device based on the selectedwinding ratio and the determined rotational speed of the chuck.